Semiconductor chips are routinely manufactured and coated in one or more locations and then transferred to transportation structures for transport to a distant location for incorporation into electronic packages or devices. Semiconductor chips are formed from wafers. If the semiconductor chips are laser emitters, the completed wafers are scribed and broken into laser bars. The edges of the laser bars are then coated with a dielectric, semi-reflective coating, usually accomplished in an evaporator. The coated bars are then unloaded into waffle packs or onto an adhesive tape. The bars are then electrically tested and then reloaded into the waffle packs or onto the tape. Then the bars are scribed and broken into individual chips. The chips are then placed on an adhesive tape for inspection in an inspection machine, usually with the p contact side facing up. Generally, the adhesive tape is mounted on a supporting hoop.
The hoop is mounted, with the p-contact side of the chips facing up, in a pick and place machine. The pick and place machine is indexed to the first chip. The p-contact side of that chip is inspected on the hoop by an overhead camera looking downwardly. A vacuum collet then picks up the chip and moves it over an upwardly looking camera to inspect the n-contact side. Good chips, namely those chips that pass these two visual inspections of the n- and p-contact sides, are placed in a waffle pack with the p-contact side facing up.
Generally, chips are processed with the p contact facing up. Oftentimes, customers of such chips have a bonding orientation which is p contact down. Thus, each of the chips must be flipped over. It is impractical to flip each chip individually. As noted above, pick and place equipment lodges the chips in a waffle pack. To flip the chips, a second waffle pack is placed in a mirror relationship with the first waffle pack and the waffle packs are flipped to obtain the proper orientation, as shown in FIGS. 12-15.
Specifically, as shown in FIG. 12, a waffle pack 100, having a top side 102 and a bottom side 104, includes a plurality of recessed portions into which chips 40 are placed. The chips 40 have a p contact side 42 and an n contact side 44, and are placed in the recessed portions with the p contact side 42 facing upwardly. A second waffle pack 110, having a top side 112 and a bottom side 114, is positioned over the first waffle pack 100 (FIG. 13) such that the top sides 102, 112 face one another. A piece of adhesive 120 may be placed between the waffle packs 100, 110.
A vacuum may be introduced to the waffle pack 100 in the direction of arrows J. The vacuum creates a pulling force on the adhesive 120 such that the surface 122 of the adhesive 120 comes in contact with and adheres to the semiconductor chips 40. With reference to FIG. 14, after the vacuum has caused the chips 40 to adhere to the adhesive 120, the second carrier 110 is moved away from the carrier 100 in the direction of arrows H. With reference to FIG. 15, the second carrier 110 is re-inverted such that the semiconductor chips 40 are positioned above the surface 122 of the adhesive 120 with the n contact side 44 up.
Alternatively, the waffle packs 100, 110 without the interspersed adhesive 120 can be flipped, thereby causing the chips 40 to move by gravity into residence in the recessed portions of the waffle pack 110 with the n contact side 44 up.
Waffle pack flipping has deficiencies, including spillage of chips and the need for additional manipulation of the chips within the waffle pack, such as, for example, with tweezers or sharpened prods.